Each year millions of Americans develop painful temporomandibular disorders (TMD) and three-quarters of them experience other regional pain syndromes. While this suggests shared etiology among pain conditions occurring at distinct anatomic sites, health care providers who treat one regional pain condition often are at a loss to manage symptoms occurring elsewhere in the body. Instead, many patients are referred from one specialist to another at great expense, but with little opportunity for coordinated care to address the underlying biopsychosocial etiology of their pain. Preliminary studies reveal shared molecular signatures among individuals with overlapping pain conditions. Compared to pain-free controls, those with overlapping pain conditions exhibited: 1) a more severe imbalance in pro- and anti-inflammatory cytokines; 2) alterations in expression of microRNAs that regulate cytokines as well as other pain-relevant targets; and 3) differences in single nucleotide polymorphisms (SNPs) located in cytokine genes. In response to PA-14-244, we plan to extend our preliminary findings through analysis of stored biospecimens and data from an existing epidemiologic study of TMD. Our investigative team comprises a molecular biologist, an epidemiologist, and a bioinformatist, with the overall goal to identify biopsychosocial factors contributing to TMD and five overlapping pain conditions: tension-type headache, low back pain, irritable bowel syndrome, pelvic pain, and widespread bodily pain. We hypothesize that protein and microRNA expression profiles, which are altered in genetically- susceptible individuals, distinguish among TMD cases and controls, with and without overlapping pain. The epidemiologic study, Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA; W. Maixner, G. Slade, Co-PDs), recruited 4,346 adults aged 18-44 years from four U.S. study sites. For this proposal, we created a case-control study design by selecting 1,460 participants: 730 with TMD and 730 without; 773 of them have ?1 overlapping condition while 687 have none. Using stored plasma samples collected from these participants, we will measure the expression of 350 proteins and 754 microRNAs by custom protein microarrays and microfluidic cards, respectively. The new data will be combined with existing genotypes from a custom platform measuring SNPs in the 350 genes encoding the same proteins as well as with characteristics of clinical pain and related biopsychosocial risk factors. We will apply conventional epidemiologic methods of mediation analysis to investigate single pathways and exploratory bioinformatics techniques to discover multivariable pathways through which biomarkers influence clinical pain. By combining these new biological markers with existing genetic and psychosocial measures from OPPERA, we expect to identify novel etiologic pathways to aid in diagnosis and treatment of TMD and overlapping pain conditions. Furthermore, the findings should point to novel targets for the development of effective therapeutics for maladaptive overlapping pain conditions.